Drying apparatus



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Filed Sept. '7, 1934 June 18, A. w. FERRE DRYING APPARATUS Filed Sept.7, 1954 2 Sheets-Sheet 2 Patented June 18, 1935 UNITED sTATEs DRYINGAPPARATUS Albert W. Ferre, Wellesley, Mass., assigner to B. F.Sturtevant Company, Inc., Boston, Mass.

Application rSeptember 7, 1934, Serial No. 743,070 3 Claims. (Cl.S21-48)' 'I'his invention, relates to drying apparatus, and relates moreparticularly to means for maintaining a desired air balance betweendrying air and air external a drier.

In drying systems of the type where it is customary to passcontinuously, through drying air, sheet material or wires, for example,which have previously been coated with some form of coating material,the problem of preventing the escape of the ydrying air has beenserious. In some cases, the vapor given off from -the coated material inthe drying operation is explosive, and, obviously, it is undesirable forsuch vapor to be vented to the atmosphere.

The difculty of preventing the escape of the drying air and the vaporcarried thereby in all drying systems, where the material is coatedexterior of the drier and is passed into the drier, is that the dryingair vand the vapor carried thereby escape through the same openingsthrough which the material to be dried enters and leaves the dryingchamber. Since the static pressure exists within the drier, some of theair and vapor escapes regardless of how small the opening for thepassage of the material is made.

According to a feature of this invention, the drying air under staticpressure in the drying chamber passes through the outer nozzle of aninjector type venturi, and the material to be `dried is caused to passthrough the inner or induced air ow nozzle of the same injector. Thedrying air under static pressure thus tends to induce air iiow externalthe drying chamber into the chamber with the entering or leaving coatedmaterial to be dried, the inflow of external air forming an eiective airseal for preventing the escape of the drying air and any vapor carriedthereby.

According to another feature of this invention,

the injector nozzles are made adjustable so that a perfect air balancewill be maintained where desired. The injector action is regulated untilno air flows in through the opening vprovided for the material, and noair or vapor flows outl for the passage of the coated material, theindrawn air providing make-up air, which may be of the chamber.

Another object of the invention is to provide a Venturi air seal for thepassage of coated materials in or out of a drying chamber.

Another object of the invention is, where desirable, to maintain an airseal at the points of passage of coated material in or out .of thedrying chamber, which prevents the escape of drying air and vaporcarried thereby, and the entrance of 15 external air.

Other objects of the invention will be apparent from the followingdescription, taken together with the drawings.

The invention will now be described with ref- 20 erence to the drawings,of which:

Fig. 1 is a view, partially in section, of a vertical tower drierprovided With the Venturi air seals or locks, according to thisinvention;

Fig. 2 is a sectional view along the lines 2-2 25 of Fig. 1; t

Fig. 3 is a sectional view along the lines 3--3 of Fig. 1;

Fig. 4 is as ectional view along the lines 4 of Fig. 3;

Fig. 5 is a partial, sectional view along the lines 5-5 of Fig. 3;

Fig. 6 is a partial, sectional view along the lines 6-6 of Fig. 3;

Fig. 7 is a plan view, partially in section, of 35 drying apparatusaccording to this invention, for the drying of sheet material, and is ofthe horizontal type;

Fig. 8 is a sectional view along the lines 8-8 of Fig. 7;

Fig. 9 is a sectional view along the lines 9-9 of Fig. '7, and

Fig. 10 is a sectional view along the lines Ill-I0 of Fig. 9.

The vertical tower drier of Figs. 1 to 6 inclu- 45 sive is of the typein which a copper wire, for example, is rst coated with an insulatingmaterial, then `passed through the drier, is again coated, and againpassed through the drier, this being repeated for a number oftimes. Thisform of towerdrier is well known to those skilled in the art, and soonly those elements necessary for an understanding of the presentinvention have been illustrated by the drawing. It is believed sucientto say that the wire I2, which enters and passes from the drying chamberI3, is a continuous wire which is coated and dried in a number ofstages. The wire I2 is thus sprayed by apparatus (not shown) and entersthe channel 4 at the lower left hand corner of Fig. 1passes upwardlythrough the channel I4, and from the drying chamber through the venturiI6, which is shown at the upper left hand corner of Fig. l. Duringpassage through the channel I4, the wireis subjected to heated air,which enters from a source (not shown) through the air duct I5. The wireis then coated and has its direction reversed by apparatus (not shown),and it again enters the drying chamber I3 through the venturi II,following which it passes through the drying chamber in the secondchannel I4, which is also supplied with heated air from duct I5, andthen passes from the lower portion of the drying chamber |3, where itagain has its direction reversed and is coated, and again enters anotherchannel I4 of the drying chamber, and passes through a third venturi I8,and so on, there being, in the particular embodiment illustrated by thedrawings, sixteen drying chambers I4 and sixteen Venturi nozzles at theupper portion of the drying chambers, similar to nozzles I6, |`I and I8.These nozzles will now be described with reference to Figs. 2 to 6inclusive.

Referring now to Fig. 2, the air flow through th duct I5 enters thechamber I4 at the upper portion, through the grille I9, and passestherefrom at its lower portion through the grille 20, into arecirculated air passage 2|.

Referring now to Fig. 3, it is seen that the air flow through the ductI5 passes through the outer injector nozzle 22 and induces air flow inthe usual injector nozzle through the inner injector nozzle 23. The wireto be dried passes from the drying chamber I3 through the center of theinner nozzle 23. The drying air and any induced air from external thedrying chamber then passes into the channel I4 in which the coated wireis subjected to the drying action of the air.

Figs. 4, 5 and 6 illustrate the parallel arrangement of the plurality ofinjector nozzles arranged at the upper portion of the vertical tower,drying chamber I3.

The injector nozzles are adjustable to enable external air to be indrawnor to enable a perfect balance between external and internal air to bemaintained. This may be accomplished by moving the inner nozzle 23 up ordown with respect to the outer nozzle 22, by manipulation of the nut 2-Iand lock nut 25 upon the threaded portion 26 of the inner nozzle 23.When the inner nozzle 23 is moved nearer the outer nozzle 22, thedistance between the tip of the nozzle 23 and the converging walls ofthe nozzle 22 decreases. The drying air which produces the injectoreffect, passes through the space beween the tip of the nozzle 23 and theconverging walls 22 and as this space decreases in area, the velocity ofthe drying air passing therethrough, consequently increases, therebyexerting a greater inducing effect upon the flow of external air throughthe nozzle 23.

Since the drying air is under static pressure, its tendency is to escapethrough nozzle 23, which it would do, were not the injector arrangementaccording to this invention, provided. Consider the nozzle 23 adjustedto its uppermost position. Then, the space between the tip of the nozzle23 and the converging walls of its associated nozzle 22 is so great, thevelocity of the drying air passing through this space so small and thenjectOr force so weak that the dryingair will ordinarily escape throughthe nozzle 23, thus preventing any entry of external air.

Now consider that the nozzle 23 is adjusted to its lowermost position.Then the space between the tip of the nozzle 23 is so small, thevelocity of the drying air through this space so great and the injectoreffect so large that the flow of external air would be induced throughthe nozzle 23.

The upper and lower limits of the nozzle 23 are so chosen with respectto the pressure of the drying air and other factors to be considered,that at the lower limit of the nozzle movement, external air would bedrawn into the system: at the upper limit of adjustment, the drying airwould escape; and at some intermediate point, the location of whichobviously depends upon the static pressure of the drying air and otherphysical factors involved, the inducing effect of the injector tendingto draw in externalair will balance the tendency of the drying air dueto its being under pressure to escape through the nozzle 23. In theparticular embodiment illustrated, it was perferred to maintain a heatbalance to prevent heat losses. If external air was drawn into thedrying chamber, it would dilute the heated air and, of course, beingcooler than the heated air, would cause heat losses. In other dryingsystems, it may be perferred to draw in outside air for use as make-upair, or for other reasons, and so this may be accomplished by adjustmentof the injector nozzle. If desired, this also may be accomplished byvariation in the static pressure of the air supplied through the ductI5, but this is ordinarily not desirable.

The inflow of the external air into the lower portion of the dryingchamber I3, through the small openings 2'I through which the wirel I2passes into and out of the lower portion of the drying chamber, isprevented by the downward flow of the heated air in the directionopposing the entrance of outside air. The drying air is not undersuflicient static pressure to cause it to pass through the smallopenings 21, especially in view of the fact that an easier path for itis provided through the grille 20 into the recirculated air passage 2|.If desired, of course, the injector devices according to this inventioncould be used at the openings 21 in the lower portion of the chamber I3,and this may be desirable where conditions justify same.

Figs. 7 to 10 inclusive illustrate the application of the invention to adrying system of the horizontal type in which coated sheet material isdried. For example, brous sheet material may be coated with pyroxalin,and then dried. The upper portion of Fig. '7 comprises the usual blower30 for forcing air through the system', the condenser 3| for enablingvaluable material inthe the heaters 32, etc'.

The material to be dried enters the drying l chamber 33 as follows:Cloth from the roll 34 passes through the sprayer 35 and thence into thedrying chamber 33 through the venturi 33.

It then passes through one section of the dryingl the venturi 45, overthe rollers 46 and 41, and then is rewound on the roll 48.

Heated air is forced by the fan 30 through the duct l) and thence, rstinto the channel 5l, from which a portion enters the channel 52, andthen into the outer nozzle 53 of the venturi 36 to tend to induceairflow through the inner nozzle 54 of the venturi, through which thesheet material 55 to be dried passes.

Another portion of air from the channel 5| passes into a channel 56,which is similar to channel 52, but located at the other end of thedrier, and which supplies air for injector purposes to the venturi 31.

Another portion of the air from the channel 5l passes through theopenings 51, at each end of the drier, and then passes into the channel58, through which the material 55 passes and serves to dry the coatedmaterial.

The duct 5U, in like manner, supplies air through opening 59 intochannel 60, and from which a portion passes into the channel 6l tooperate the venturi 45, and into the channel 62 to operate the venturi42, and another portion of which passes through the openings 63 and 64to dry the coated material passing therebeneath.

Finally, the duct 50 supplies, through the opening 65 and into thechannel 66, drying air, which passes from the opening 61 to dry thecoated material passing thereabove, and through the opening 68 to drythe coated material passing therebelow. A portion of the drying air isdrawn, by action of fan 30, into the recirculated air inlets 69, andthence into the recirculated air duct 10, and in contact again withtheheaters 32'. Another portion of the drying air is drawn in through theopenings 1I into the duct 12 and thence through the condenser 3 I, wheresuflicient of the vapors collected by it may be condensed to enable thedrying air, in its next circuit through the drying chamber, to dry thecoated material.

The Venturi or injector nozzles shown by Figs. 7 to 10 inclusive areadjustable in the same way as those described in connection with Figs. 1to 6 inclusive are, in order that they may be made to maintain a balancebetween the drying air and external air at the openings through whichthe coated material passes in and out of the drying chamber, or one ormore of the venturis may be adjusted to draw external air into thedrying chamber to provide make-up air. When external air is drawn intothe drying chamber, a portion of the drying air may be exhausted to theatmosphere through the vent 13.

Whereas the invention has been described in connection with coatedmaterials, it should be understood that it applies equally well to thedrying of other materials. For example, the invention may be used in thedrying of sheets formed from cellulose materials, such as paper,artificial cloth, or the like, and may also be used in textile mills,orin any other system where material previously treated is passed intoo1' o'ut of a drying chamber into which a conditioned vapor for dryingpurposes is supplied.

Whereas several embodiments of the invention have been described for thepurpose of illustration, it should be understood that the invention isnot limited to the details described, since many modications may be madeby those skilled in the art without departing from the spirit of theinvention.

What is claimed is:

l. Drying apparatus comprising a drying chamber, means for providingdrying air under static pressure within said chamber, an opening in saidchamber through which material under treatment passes, means utilizingdrying air for inducing the flow inwardly through said opening ofatmospheric air, and means for adjusting the effect of said lastmentioned means to induce the flow of external air into said chamber orto`produce a balance between the drying air in said chamber andatmospheric air external said chamber to prevent the iiow of drying airthrough said opening and the flow of .atmospheric air through saidopening.

2. Drying apparatus comprising a drying chamber, means for providingdrying air under static pressure within said chamber, an opening in saidchamber through which material under treatment passes, a Venturi in saidopening, means for conducting atmospheric air outside said chamberthrough said opening to said venturi, means for directing drying airthrough said venturi to induce the inward flow through said opening ofatmospheric air, and means for adjusting the velocity of drying airflowing through said venturi to vary the volume of flow of external airthrough said opening into said chamber.

3. Drying apparatus comprising a drying chamber, means for providingdrying air under static pressure within said chamber, an opening in saidchamber through which material under treatment passes, a venturi withinsaid opening, a nozzle within said opening for conducting atmosphericair outside said chamber to said venturi, means for directing drying airthrough said venturi to induce the inward flow through said nozzle ofatmospheric air, and means for varying the distance between the tip ofsaid nozzle and said venturi to vary the inducing effect of said dryingair upon atmospheric air external said opening.

ALBERT W. FERRE.

